In semiconductor manufacturing, optical metrology is typically used for measuring and evaluating properties such as optical properties, shapes of nano patterns, and the like, of nano samples in real time in a non-destructive manner or a non-contact manner. For example, a measuring process may be performed to measure a dimension (e.g., thickness, line width, etc) of a structure formed on a wafer.
Spectroscopic ellipsometry (SE) may be used to calculate a profile of the periodic pattern formed on the wafer (optical critical dimension).
However, through these measuring methods, it may be difficult to precisely measuring a thickness of a thin layer formed on a pattern due to correlation between an underlying structure.